Plasma display apparatus, fluorescent material, and fluorescent material manufacturing method

ABSTRACT

The present invention inhibits water adsorption onto the surface of a blue phosphor, decreases luminance degradation and chromaticity shift of a phosphor, or improves discharge characteristics thereof. The blue phosphor is a compound represented by Ba 1-x MgAl 10 O 17 :Eu x  or Ba 1-x-y Sr y MgAl 10 O 17 :Eu x , wherein 0.03≦x≦0.25 and 0.1≦y≦0.5, and containing at least one of Ti, Zr, Hf, Si, Ge, Sn, and Ce substituting for part of one of elements Al and Mg.

TECHNICAL FIELD

The present invention relates to a plasma display apparatus(device) usedfor image display on a television or other equipment. It also relates toa phosphor for use in the plasma display device, and a method offabricating the phosphor(fluorescent material).

BACKGROUND ART

Among color display devices used for image display on a computer ortelevision, a display device using a plasma display panel (hereinafterreferred to as a “PDP”) has recently been drawing attention, as a large,thin, and light color display device.

A plasma display device using a PDP performs additive color mixing ofso-called three primary colors (red, green, and blue) to providefull-color display. For this full-color display, a plasma display devicehas phosphor layers for emitting the respective three primary colors,i.e. red (R), green (G), and blue (B). Phosphor particles constitutingthese phosphor layers are exited by ultraviolet light generated indischarge cells of the PDP to generate visible light of respectivecolors.

Known as compounds used for the phosphors of above respective colors are(YGd)BO₃:Eu³⁺ and Y₂O₃:Eu⁺³ for red emission, Zn₂SiO₄:Mn⁺² for greenemission, and BaMgAl₁₀O₁₇:Eu⁺² for blue emission. Each of thesephosphors is fabricated by mixing specific materials and firing themixture at high temperatures of at least 1,000° C. for solid-phasereaction (see “Phosphor Handbook” p.219 and 225, Ohmsha, for example).The phosphor particles obtained by this firing are used after they aremilled and classified (average diameter of red and green particles: 2 to5 μm, average diameter of blue particles: 3 to 10 μm).

The phosphor particles are milled and classified for the followingreason. In general, when phosphor layers are formed on a PDP, atechnique of screen-printing a paste of phosphor particles of each coloris used. In application of the paste, the smaller and more uniformdiameters of phosphor particles (i.e. a uniform particle sizedistribution) can easily provide the smoother coated surface.

In other words, when phosphor particles have smaller and more uniformdiameters and shapes approximating to a sphere, the coated surface issmoother. The smoother coated surface increases the packing density ofthe phosphor particles in a phosphor layer and the emission surface areaof the particles, thus alleviating unstableness at address drive. As aresult, it is theoretically considered that the luminance of the plasmadisplay device can be increased.

However, the smaller diameters of phosphor particles increase thesurface area of the phosphor and defects on the surface of the phosphor.For this reason, a large quantity of water, carbonic acid gas, ororganic substances including hydrocarbon are likely to adhere to thesurface of the phosphor. Especially for a blue phosphor made ofBa_(1-x)MgAl₁₀O₁₇:Eu_(x), or Ba_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x), thesecrystal structures have layer structures (see “Display and Imaging”,1999, vol. 7, pp 225-234, for example). In the layers, there is oxygen(O) vacancy in the vicinity of a layers containing Ba atoms (Ba—Olayers) (see OYO BUTSURI (Applied Physics), vol. 70, No.3, 2001, pp 310,for example).

For this reason, water existing in air is selectively adsorbed onto thesurface of the Ba—O layer of the phosphor. Therefore, because a largequantity of water is released into a panel in a panel manufacturingprocess, the water reacts with the phosphor and MgO during discharge.This poses problems of luminance degradation and chromaticity shift(color shift or image burn caused by the chromaticity shift), ordecrease in drive voltage margin and increase in discharge voltage. Aconventionally devised method to address these problems is coating theentire surface of the phosphor with a crystal of Al₂O₃, in order torecover the defects in the vicinity of the Ba—O layer (see JapanesePatent Unexamined Publication No. 2001-55567, for example).

However, this method poses another problem: coating the entire surfacecauses absorption of ultraviolet light and thus decreases the emissionluminance of the phosphor, and the ultraviolet light decreases theluminance.

DISCLOSURE OF THE INVENTION

In order to address these problems, the present invention aims toinhibit water adsorption onto the surface of a blue phosphor, decreaseluminance degradation and chromaticity shift of a phosphor, or improvedischarge characteristics thereof. Especially in the present invention,elimination of oxygen vacancy in the vicinity of a layers containing Baatoms (Ba—O layers) in a blue phosphor inhibits water adsorption ontothe surface of the blue phosphor, decreases luminance degradation andchromaticity shift of a phosphor, or improves discharge characteristicsthereof.

In order to accomplish these purposes, a plasma display device of thepresent invention has a plasma display panel in which a plurality ofdischarge cells of one or a plurality of colors are disposed in arrays,phosphor layers having a color corresponding to the respective dischargecells are disposed, and the phosphor layers are excited by ultravioletlight to emit light. The phosphor layers have a blue phosphor. The bluephosphor is made of a compound represented by Ba_(1-x)MgAl₁₀O₁₇:Eu_(x)or Ba_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x) in which at least one kind of theelements Ti, Zr, Hf, Si, Ge, Sn and Ce substitutes for part of theelement Al or Mg.

A phosphor of the present invention is a blue phosphor having a crystalstructure of Ba_(1-x)MgAl₁₀O₁₇:Eu_(x) orBa_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x) that is exited by ultraviolet light toemit visible light. In the blue phosphor, a quadrivalent elementsubstitutes for the element Al or Mg that constitutes the phosphor.

A method of manufacturing a phosphor of the present invention includes:a mixed solution fabrication step in which a metal salt or organometalicsalt containing elements constituting a blue phosphor (Ba, Mg, Al, Eu,and M (where M is one kind of the elements Ti, Zr, Si, Ge, Sn and Ce ))is mixed with an aqueous medium to fabricate a mixed solution; and astep of drying the mixed solution, and thereafter firing the mixture ina reducing atmosphere to fabricateBa_(1-x)(Mg_(1-a)M_(a))(Al_(1-b)M_(b))Al₁₀O₁₇:Eu_(x) andBa_(1-x-y)Sr_(y)(Mg_(1-a)M_(a))(Al_(1-b)M_(b))Al₁₀O₁₇ (where M is atleast one kind of the elements Ti, Zr, Hf, Si, Ge, Sn and Ce ).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a plasma display panel (PDP) in accordance withone embodiment of the present invention with a front glass substratethereof removed.

FIG. 2 is a perspective view showing a partial section of a structure ofan image display area of the PDP.

FIG. 3 is a block diagram of a plasma display device in accordance withone embodiment of the present invention.

FIG. 4 is a sectional view of an image display area of a PDP inaccordance with one embodiment of the present invention.

FIG. 5 is a schematic diagram showing a structure of an ink dispenserused when phosphor layers of the PDP is formed.

FIG. 6 is a schematic diagram showing an atomic structure of a bluephosphor in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

First, a description is provided of an advantage of eliminating oxygenvacancy in the vicinity of a Ba—O layer in a blue phosphor.

A phosphor for use in a PDP or other equipment is fabricated by asolid-phase reaction method, an aqueous solution reaction method, orother methods. When a phosphor has smaller particle diameters, defectsare likely to occur. Especially for the solid-phase reaction method, itis known that milling a phosphor after firing leads many defects. It isalso known that ultraviolet light having a wavelength of 147 nmgenerated by discharge in driving a panel causes defects in a phosphor(see Electronic Information and Communication Institute, TechnicalResearch Report, EID99-94, Jan. 27, 2000, for example).

Especially for BaMgAl₁₀O₁₇:Eu, a blue phosphor, it is known that thephosphor itself has oxygen vacancy especially in a Ba—O layer thereof(see OYO BUTSURI (Applied Physics), vol. 70, No.3, 2001, pp310, forexample).

FIG. 6 is a diagram schematically showing a structure of a Ba—O layer inthe blue phosphor BaMgAl₁₀O₁₇:Eu.

For a conventional blue phosphor, existence of these defects itself hasbeen considered as a cause of luminance degradation. In other words, ithas been considered the degradation is caused by defects. Such defectsare caused by impact of ions generated in driving a panel on thephosphor and by ultraviolet light having a wavelength of 147 nm.

The inventors have found that the luminance degradation is not onlyessentially caused by existence of the defects but is caused byselective adsorption of water or carbonic acid gas to oxygen (O) vacancyin the vicinity of a Ba—O layer. By irradiating the adsorption withultraviolet light or ions, the phosphor reacts with water, thus causingluminance degradation and color shift. In other words, the inventorshave come to know that adsorption of water or carbonic acid gas tooxygen vacancy in the vicinity of a Ba—O layer in a blue phosphor causesa various kinds of degradation.

Based on this knowledge, the inventors have decreased oxygen vacancy inthe vicinity of a Ba—O layer in a blue phosphor to prevent degradationthereof in a panel manufacturing process and in driving a panel, withoutdecreasing the luminance of the blue phosphor.

In order to decrease the oxygen vacancy in the vicinity of a Ba—O layer,the inventors have substitute a quadrivalent element for part of theelement aluminum (Al) or magnesium (Mg) in a blue phosphor having acrystal structure of BaMgAl₁₀O₁₇:Eu or BaSrMgAl₁₀O₁₇:Eu.

Next, a description is provided of an advantage of substitutingquadrivalent ions for part of the element Al or Mg in BaMgAl₁₀O₁₇.

The elements Al and Mg in BaMgAl₁₀O₁₇:Eu, a blue phosphor, exist astrivalent and divalent ions, respectively. Positive electrical chargesare increased in the crystal by substituting quadrivalent positive ions,such as titanium (Ti), zirconium (Zr), hafnium (Hf), silicon (Si),germanium (Ge), tin (Sn), and cerium (Ce), for any position in thetrivalent or divalent ions. In order to neutralize these positiveelectrical charges (compensate for electrical charges), negativelycharged oxygen compensates for oxygen vacancy in the vicinity of theelement Ba. As a result, it is considered that the oxygen vacancy in thevicinity of the Ba—O layer can be decreased.

Methods of manufacturing a phosphor of the present invention aredescribed hereinafter.

As methods of manufacturing a phosphor itself, a conventionalsolid-phase firing method, a liquid-phase method, and a liquid spraymethod are considered. In the solid-phase firing method, oxide orcarbonate materials are fired using a fluxing agent. In the liquid-phasemethod, a precursor of a phosphor is fabricated using a co-precipitationmethod of hydrolyzing an organometallic salt or a nitrate in an aqueoussolution or forming precipitation by addition of an alkali, and then theprecursor is heat-treated. In the liquid spray method, an aqueoussolution containing phosphor materials is sprayed into ahigh-temperature furnace. It has been found that substitutingquadrivalent ions (Ti, Zr, Hf, Si, Ge, Sn, or Ce) for part of theelement Al or Mg in BaMgAl₁₀O₁₇:Eu is effective, in a phosphorfabricated by any method.

Next, as an example of a method of fabricating a phosphor, a descriptionis provided of a method of manufacturing a blue phosphor using asolid-phase reaction method. Carbonates and oxides, such as BaCO₃,MgCO₃, Al₂O₃, Eu₂O₃, and MO₂ (where M is Ti, Zr, Hf, Si, Ge, Sn, or Ce),as materials, are mixed with a small amount of fluxing agent (AlF₃ orBaCl₂) as a sintering agent. The mixture is fired at a temperature of1,400° C. for two hours. Then, the fired mixture is milled andclassified. Next, the milled and classified product is fired at atemperature of 1,500° C. for two hours in a reducing atmosphere (H₂(5%)-N₂ matrix), and milled and classified again to provide a phosphor.

When a phosphor is fabricated from an aqueous solution (liquid-phasemethod), organometallic salts containing elements constituting thephosphor, such as alkoxide and acetylacetone, or nitrates are dissolvedin water, and then a co-precipitate (hydrate) is obtained by hydrolysis.The hydrate is hydro-thermally synthesized (crystallized in anautoclave), fired in air, or sprayed into a high-temperature furnace toprovide fine particles. The fine particles are fired at a temperature of1,500° C. for two hours in a reducing atmosphere (H₂ (5%)-N₂ matrix) toprovide a phosphor.

Next, the blue phosphor obtained in this method is milled and classifiedto provide a phosphor.

Preferably, the substitution value of quadrivalent ions (Ti, Zr, Hf, Si,Sn, Ge, or Ce) substituting for Al or Mg ions ranges from 0.01 to 3% ofAl or Mg. For a substitution value up to 0.01%, the effect of preventingluminance degradation is small. For a substitution value of at least 3%,the luminance of the phosphor decreases. It has been recognized that thequadrivalent ions have substituted for Al or Mg ions instead of Ba or Euions because the blue emission spectrum has a wavelength of 450 nm atany substitution value.

In this manner, substituting quadrivalent ions for Al or Mg ions in acrystal of BaMgAl₁₀O₁₇:Eu using the conventional method of fabricatingblue phosphor particles can provide a phosphor resistant to water (i.e.durable against water and carbonic acid gas generated in a phosphorfiring process, panel sealing process, panel aging process, or indriving a panel) without degradation of the luminance of the bluephosphor.

A plasma display device of the present invention has a PDP in which aplurality of discharge cells of one or a plurality of colors aredisposed in arrays, phosphor layers having a color corresponding to therespective discharge cells are disposed, and the phosphor layers areexcited by ultraviolet light to emit light. Each of the blue phosphorlayer is characterized by being made of blue phosphor particles in whichquadrivalent ions (Ti, Zr, Hf, Si, Sn, Ge, or Ce) substitute for Al orMg ions in a crystal of BaMgAl₁₀O₁₇:Eu or BaSrMgAl₁₀O₁₇:Eu; that has auniform particle size distribution.

The diameters of blue phosphor particles in which quadrivalent ions (Ti,Zr, Hf, Si, Sn, Ge, or Ce) substitute for part of Al or Mg ions inBaMgAl₁₀O₁₇:Eu or BaSrMgAl₁₀O₁₇:Eu are as small as 0.05 to 3 μm. Theparticle size distribution of the blue particles is excellent. Further,when each of phosphor particles forming a phosphor layer has a sphericalshape, the packing density of the layer increases. This increases theemission area of phosphor particles substantially contributing to lightemission. The increased emission area can increase the luminance of aplasma display device and provide a plasma display device that hasinhibited luminance degradation and color shift and excellent luminancecharacteristics.

Now, it is more preferable that the average particle diameter ofphosphor particles ranges from 0.1 to 2.0 μm. As to the particle sizedistribution, it is more preferable that the maximum particle size is atmost four times of the mean value and the minimum value is at least aquarter of the mean value. In a phosphor particle, the area ultravioletlight reaches is as shallow as several hundred nm from the surface ofthe particle and only the surface thereof emits light. When the diameterof such a phosphor particle is 2.0 μm or smaller, the surface area ofthe particle contributing to light emission increases and the emissionefficiency of the phosphor layer is kept high. For a diameter of atleast 3.0 μm, the thickness of the phosphor must be at least 20 μm and asufficient discharge space cannot be ensured. For a diameter up to 0.1μm, defects are likely to occur and the luminance does not increase.

When the thickness of a phosphor layer is set to 8 to 25 times of theaverage diameter of phosphor particles, a sufficient discharge space canbe ensured while the emission efficiency of the phosphor layer is kepthigh. Therefore, the luminance of a plasma display device can beincreased. Especially when the average particle diameter of a phosphoris up to 3 μm, this effect is greater (see The Institute of ImageInformation and Television Engineers, IDY2000-317, pp32).

A specific example of phosphor particles used for blue phosphor layersin a plasma display device is made of a compound represented byBa_(1-x),MgAl₁₀O₁₇:Eu_(x) or Ba_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x). Whenvalues X and Y in these compounds are such that 0.03≦X≦0.20 and0.1≦Y≦0.5, the blue phosphor layers have a high luminance. Thus,satisfying these conditions is preferable.

A specific example of phosphor particles used for red phosphor layers ina plasma display device is made of a compound represented byY_(2-x)O₃:Eu_(x) or (Y,Gd)_(1-x)BO₃:Eu_(x). When value X in thecompounds of the red phosphor is such that 0.05≦X≦0.20, the red phosphorlayers have an excellent luminance and resistance to luminancedegradation. Thus, satisfying this condition is preferable.

A specific example of phosphor particles used for green phosphor layersin a plasma display device is made of a compound represented byBa_(1-x)Al₁₂O₁₉:Mn_(x) or Zn_(2-x)SiO₄:Mn_(x). When value X in thecompounds of the green phosphor is such that 0.01≦X≦0.10, the greenphosphor layers have an excellent luminance and resistance to luminancedegradation. Thus, satisfying this condition is preferable.

A method of manufacturing a plasma display panel of the presentinvention is characterized by having a disposing step, firing step andsealing step. In the disposing step, pastes are disposed on a substrateof a first panel. Each kind of the pastes is made of phosphor particlesin which quadrivalent ions substitute for Al or Mg ions in the bluephosphor Ba_(1-x)MgAl₁₀O₁₇:Eu_(x) or Ba_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x),red phosphor particles, or green phosphor particles, and a binder. Inthe firing step, the binder included in each kind of the pastes disposedon the first panel is burnt out. In the sealing step, the first panelhaving the phosphor particles disposed on the substrate by the firingstep, and a second panel are placed one on the other, and sealed. Thesesteps can provide a plasma display device having an excellent luminanceand resistance to luminance degradation.

The phosphor of the present invention can also be applied to fluorescentlighting. In this case, the fluorescent lighting is characterized byhaving a phosphor layer that is excited by ultraviolet light to emitvisible light, and the phosphor layer is made of phosphor particles eachhaving water repellent finish on the surface thereof. This structure canprovide fluorescent lighting that has phosphor particles havingexcellent light emission characteristics, luminance, and resistance toluminance degradation.

A plasma display device in accordance with one embodiment of the presentinvention is described hereinafter with reference to the accompanyingdrawings.

FIG. 1 is a schematic plan view of a PDP with a front glass substratethereof removed. FIG. 2 is a partially sectional view in perspective ofan image display area of the PDP. In FIG. 1, the number of displayelectrodes, display scan electrodes, and address electrodes is reducedto facilitate explanation. With reference to these FIGS. 1 and 2, thestructure of a PDP is described.

As shown in FIG. 1, PDP 100 includes front glass substrate 101 (notshown), rear glass substrate 102, N display electrodes 103, N displayscan electrodes 104 (Nth electrode indicated by N), M address electrodes107 (Mth electrode indicated by M), and hermetic seal layer 121 shown byoblique lines. The PDP has an electrode matrix having a three-electrodestructure made of respective electrodes 103, 104, and 107. Respectivecells are formed at the respective intersections of display scanelectrodes 104 and address electrodes 107.

As shown in FIG. 2, this PDP 100 is structured so that a front panel anda rear panel are assembled together and discharge space 122 formedbetween the front panel and the rear panel is filled with a dischargegas. In the front panel, display electrodes 103, display scan electrodes104, dielectric glass layer 105, and MgO protective layer 106 aredisposed on a principal surface of front glass substrate 101. In therear panel, address electrodes 107, dielectric glass layer 108, barrierribs 109, and phosphor layers 110R, 110G and 110B are disposed on aprincipal surface of rear glass substrate 102. In phosphor layers 110B,a quadrivalent element substitutes for the element Al or Mg in a bluephosphor.

When an image is displayed on a plasma display device, first, displaydriver circuit 153, display scan driver circuit 154, and address drivercircuit 155 are connected to PDP 100, as shown FIG. 3. Next, accordingto control of controller 152, a signal voltage is applied across displayscan electrode 104 and address electrode 107 of a cell to be lit foraddress discharge therebetween. Then, a pulse voltage is applied acrossdisplay electrode 103 and display scan electrode 104 for sustaindischarge. This sustain discharge generates ultraviolet light in thecell. The phosphor layer excited by this ultraviolet light emits light,thus lighting the cell. Combination of lit and unlit cells of therespective colors provides image display.

Next, a method of manufacturing this PDP 100 is described with referenceto FIGS. 4 and 5.

(1) Production of Front Panel

First, N display electrodes 103 and N display scan electrodes 104 arearranged on front glass substrate 101 alternately, in parallel with eachother, like stripes. (In FIG. 2, only two of respective electrodes areshown for simplicity.) Thereafter, the electrodes are covered withdielectric glass layer 105, and MgO protective layer 106 is furtherformed over the surface of dielectric glass layer 105.

Display electrodes 103 and display scan electrodes 104 are made ofsilver. These electrodes are formed by applying a silver paste forelectrodes by screen-printing and firing the paste.

Dielectric glass layer 105 is formed by applying a paste containing leadglass material by screen-printing, and firing the paste at a specifiedtemperature for a specified period of time (e.g. at 56° C. for 20 min.)so that the layer has a specified thickness (approx. 20 μm). Examples ofthe paste containing lead glass material to be used include a mixture ofPbO (70 wt %), B₂O₃ (15 wt %), SiO₂ (10 wt %), Al₂O₃ (5 wt %) and anorganic binder (α-terpineol containing 10% of ethyl cellulose dissolvedtherein).

The organic binder contains a resin dissolved in an organic solvent.Acrylic resin can be used as a resin other than the ethyl cellulose, andn-butylcarbitol as an organic solvent. Further, a dispersion agent (e.g.glyceryl trileate) can be mixed into such an organic binder.

MgO protective layer 106 is made of magnesium oxide (MgO). The layer isformed by sputtering method or chemical vapor deposition (CVD) method,for example, to have a specified thickness (approx. 0.5 μm).

(2) Production of Rear Panel

First, M address electrodes 107 are formed in lines by screen-printing asilver paste for electrodes on rear glass substrate 102 and firing thepaste. Next, dielectric glass layer 108 is formed by applying a pastecontaining lead glass material to the address electrodes by ascreen-printing method. Barrier ribs 109 are formed by repeatedlyapplying the same paste containing lead glass material to the dielectricglass layer by the screen-printing method at a specified pitch andfiring the paste. These barrier ribs 109 partition discharge space 122into respective cells (unit emission area) in the direction of thelines.

FIG. 4 is a partially sectional view of PDP 100. As shown in thedrawing, interval dimension W between barrier ribs 109 is specified to avalue ranging from approx. 130 to 240 μm, according to a HDTV screenhaving a diagonal size ranging from 32 to 50 in.

Paste-like phosphor ink made of red (R), green (G), or blue (B) phosphorparticles and an organic binder is applied to grooves between barrierribs 109, and fired at temperatures ranging from 400 to 590° C. to burnout the organic binder. Thus, phosphor layers 110R, 110G, and 110B inwhich phosphor particles of corresponding colors are bound are formed.In the blue phosphor particles, quadrivalent element ions substitute forAl or Mg element ions in Ba_(1-x)MgAl₁₀O₁₇:Eu_(x) orBa_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x).

It is preferable that thickness L of each of these phosphor layers 110R,110G, and 110B on address electrode 107 in the direction of laminationis approx. 8 to 25 times of the average diameter of the phosphorparticles of each color. In other words, in order to ensure a certainluminance (emission efficiency) when a phosphor layer is irradiated witha specified amount of ultraviolet light, the phosphor layer needs toabsorb ultraviolet light generated in the discharge space instead ofallowing it to pass through. For this purpose, it is desirable that thephosphor layer has a thickness in which at least eight layers,preferably, approx. 20 layers are laminated. For a thickness larger thanthat, the emission efficiency of the phosphor layer is almost saturated.Further, for a thickness exceeding lamination of approx. 20 layers,sufficiently large discharge space 122 cannot be ensured.

Phosphor particles having sufficiently small diameters and sphericalshapes, like those obtained by hydrothermal synthesis or other methods,have a packing factor of the phosphor layer and a total surface area ofthe phosphor particles larger than those of phosphor particles havingnon-spherical shapes, even when the number of laminated layers are thesame. As a result, for phosphor particles having spherical shapes, thesurface areas thereof contributing to actual light emission of thephosphor layer are increased and the emission efficiency is furtherincreased. Descriptions are given later of a method of synthesizingthese phosphor layers 110R, 110G, and 110B, and a method of fabricatingblue phosphor particles for use in the blue phosphor layer employingsubstitution of quadrivalent ions.

(3) Production of PDP by Assembly Panels

The front panel and the rear panel produced in this manner are placedone on the other so that respective electrodes on the front panel areorthogonal to the address electrodes on the rear panel. A sealing glassis inserted between the panels in the periphery thereof and fired at atemperature of approx. 450° C. for 10 to 20 min., for example, to fromhermetical seal layer 121 (see FIG. 1) for sealing. Next, dischargespace 122 is once evacuated to a high vacuum (e.g. 1.1×10⁻⁴ Pa) andfilled with a discharge gas (e.g. He—Xe or Ne—Xe inert gas) at aspecified pressure, to provide PDP 100.

(4) A Method of Forming Phosphor Layers

FIG. 5 is a schematic diagram showing a structure of ink dispenser 200for use in forming phosphor layers 110R, 110G, and 110B. As shown inFIG. 5, ink dispenser 200 includes server 210, pressure pump 220, andheader 230. Phosphor ink is pressurized by pressure pump 220 andsupplied from server 210 for storing the phosphor ink to header 230.

The ink dispenser is structured so that header 230 has ink chamber 230 aand nozzle 240, and the phosphor ink pressurized and supplied to inkchamber 230 a is continuously ejected from nozzle 240. It is desirablethat bore diameter D of this nozzle 240 is set to at least 30 μm inorder to prevent clogging of the nozzle. It is also desirable that borediameter D is equal to or smaller than interval W between barrier ribs109 (approx. 130 to 200 μm) in order to prevent displacement of aphosphor layer from the barrier ribs in application. Thus, bore diameterD is generally set to 30 to 130 μm.

Header 230 is structured to be driven lineally by a header scanningmechanism (not shown). Continuously ejecting phosphor ink 250 fromnozzle 240 and scanning header 230 at the same time allows the phosphorink to be uniformly applied to the grooves between barrier ribs 109 onrear glass substrate 102. Viscosity of the phosphor ink used in thisembodiment is kept within the range of 1,500 to 3,000 centipoises (CP)at a temperature of 25° C.

This server 210 also has a mixer (not shown). Mixing preventsprecipitation of particles in phosphor ink. Header 230 is integrallyformed with ink chamber 230 a and nozzle 240 by performing machining andelectric discharge machining on a metallic material.

The methods of forming phosphor layers are not limited to the abovemethod. Other various kinds of usable methods include photolithography,screen-printing, and a method of disposing a film including phosphorparticles mixed therein.

The phosphor ink is prepared by mixing phosphor particles of each color,a binder and a solvent so that the mixture has a viscosity ranging from1,500 to 3,000 centipoises (CP). A surface-active agent, silica, adispersant agent (0.1 to 5 wt %) can also be added, as required.

Used as a red phosphor included in this phosphor ink is a compoundrepresented by (Y,Gd)_(1-x)BO₃:Eu_(x) or Y_(2-x)O₃:Eu_(x). In thesecompounds, the element Eu substitutes for part of the element Yconstituting the matrix of the compounds. It is preferable that thesubstitution value X of the element Eu with respect to the element Y is0.05≦X≦0.20. For a substitution value larger than this value, thephosphor has a high luminance but considerable luminance degradation.For this reason, it is considered that the red phosphor cannot be usedpractically. For a substitution value smaller than this value, thecomposition ratio of Eu mainly emitting light is small and thus theluminance decreases. Therefore, the red phosphor cannot be used as aphosphor.

Used as a green phosphor is a compound represented byBa_(1-x)Al₁₂O₁₉:Mn_(x) or Zn_(2-x)SiO₄:Mn_(x). Ba_(1-x)Al₁₂O₁₉:Mn_(x) isa compound in which the element Mn substitutes for part of the elementBa constituting the matrix of the compound. Zn_(2-x)SiO₄:Mn_(x) is acompound in which the element Mn substitutes for part of the element Znconstituting the matrix of the compound. It is preferable that thesubstitution value X of the element Mn with respect to the elements Baand Zn is 0.01≦X≦0.10 for the reason described in the case of the redphosphor.

Used as a blue phosphor is a compound represented byBa_(1-x)MgAl₁₀O₁₇:Eu_(x) or Ba_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x).Ba_(1-x)MgAl₁₀O₁₇:Eu_(x) and Ba_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x) arecompounds in which the element Eu or Sr substitutes for part of theelement Ba constituting the matrix of the compounds. It is preferablethat the substitution value X of the element Eu and substitution value Yof the element Sr with respect to the element Ba are 0.03≦X≦0.20 and0.1≦Y≦0.5, respectively, for the reason described in the above case.

It is also preferable that the substitution values of quadrivalent ions(Ti, Zr, Hf, Si, Ge, Sn, or Ce) substituting for the element Al or Mg is0.001≦a≦0.03 and 0.001≦b≦0.03, inBa(Mg_(1-a)M_(a))(Al_(1-b)M_(b))₁₀O₁₇:Eu_(x). In other words, it ispreferable that the substitution values ranges from 0.1 to 3%.

Ethyl cellulose or acrylic resin can be used as a binder included inphosphor ink (in an amount of 0.1 to 10 wt % of the ink) and α-terpineolor n-butylcarbitol can be used as a solvent. Polymers, such as PMA andPVA, can also be used as a binder, and organic solvent, such asdiethyleneglycol and methyl ether, can also be used as a solvent.

The phosphor particles used in this embodiment are manufactured by asolid-phase firing method, aqueous solution reaction method, sprayfiring method, or hydrothermal synthesis method.

(1) Blue Phosphor

Ba_(1-x)MgAl₁₀O₁₇:Eu_(x)

First, in a mixed solution fabrication process, materials, i.e. bariumnitrate (Ba(NO₃)₂), magnesium nitrate (Mg(NO₃)₂), aluminum nitrate(Al(NO₃)₃), and europium nitrate (Eu(NO₃)₂) are mixed in a molar ratioof Ba(NO₃)₂:Mg(NO₃)₂:Al(NO₃)₃:Eu(NO₃)₂=1-X:1:10:X (0.03≦X≦0.25). Thismixture is dissolved in an aqueous medium to provide hydrate mixedsolution. As this aqueous medium, ion-exchange water or pure water ispreferable because they contain no impurities. However, non-aqueoussolvent (e.g. methanol and ethanol) can be contained in the aqueousmedium.

Used as materials for substituting quadrivalent ions (Ti, Zr, Hf, Si,Sn, Ge, or Ce) for Mg or Al are nitrates, chlorides, or organiccompounds of the quadrivalent ions. As for the substitution values ofthe materials, the materials are mixed to provide 0.001≦a and b≦0.03 in(Mg_(1-a)M_(a))(Al_(1-b)M_(b)) where M is a quadrivalent ion.

Next, the hydrate mixed solution is held in a container made of acorrosion- and heat-resistant material, such as gold and platinum. Thenthe mixed solution is hydro-thermally synthesized for 12 to 20 hours, atspecified temperatures (100 to 350° C. under specified pressures (0.2 to25 MPa), in a high pressure vessel, using equipment capable of heatingand pressurizing at the same time, such as an autoclave.

Next, these particles are fired in a reducing atmosphere containing 5%of hydrogen and 95% of nitrogen, for example, at a specified temperaturefor a specified period of time (e.g. at 1,350° C. for two hours).Thereafter, the fired particles are classified to provide a desired bluephosphor, Ba_(1-x)MgAl₁₀O₁₇:Eu_(x), in which quadrivalent ionssubstitute for part of the elements Mg or Al.

The phosphor particles obtained by hydrothermal synthesis have sphericalshapes and an average particle diameter ranging from approx. 0.05 to 2.0μm, which is smaller than that of particles fabricated by theconventional solid-phase reaction method. Now, the term “spherical” asused herein is defined so that the aspect ratios (minor axisdiameter/major axis diameter) of most of the phosphor particles rangefrom 0.9 to 1.0, for example. Not all the phosphor particles need tofall within this range.

The hydrate mixture can be sprayed from a nozzle into a high-temperaturefurnace to synthesize a phosphor instead of being held in a gold orplatinum container. This method is known as a spray method and the bluephosphor can also be manufactured by the spray method.

Ba_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x)

This phosphor is made of materials different from those of the aboveBa_(1-x)MgAl₁₀O₁₇:Eu_(x), and fabricated by a solid reaction method. Thematerials used are described hereinafter.

The materials, i.e. barium hydroxide (Ba(OH)₂), strontium hydroxide(Sr(OH)₂), magnesium hydroxide (Mg(OH)₂), aluminum hydroxide (Al(OH)₃),and europium hydroxide (Eu(OH)₂) are weighted in a required molar ratio.Next, oxides or hydroxides containing quadrivalent ions (Ti, Zr, Hf, Si,Ge, Sn, or Ce) for substituting for Mg or Al are weighted in a requiredratio. These materials are mixed together with AlF₃, a fluxing agent.The mixture is fired at specified temperatures (1,300 to 1400° C.) forspecified periods of time (12 to 20 hours.) Thus,Ba_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x) in which quadrivalent ions substitutefor Mg or Al can be obtained. The average diameter of the phosphorparticles obtained by this method ranges from approx. 0.1 to 3.0 μm.

Next, the phosphor is fired in a reducing atmosphere (containing 5% ofhydrogen and 95% of nitrogen, for example) at specified temperatures(1,000 to 1,600° C.) for two hours, and thereafter classified by an airclassifier to provide phosphor particles. Mainly used as the materialsof the phosphor are oxides, nitrates, and hydroxides. However, thephosphor can also be fabricated using organometallic compoundscontaining the elements Ba, Sr, Mg, Al, Eu, Ti, Zr, Hf, Si, Sn, Ge, andCe, such as metal alkoxide and acethylacetone.

(2) Green Phosphor

Zn_(2-x)SiO₄:Mn_(x)

First, in a mixed solution fabrication process, materials, i.e. zincnitrate (Zn(NO₃)), silicon nitrate (Si(NO₃)₂), and manganese nitrate(Mn(NO₃)₂) are mixed in a molar ratio ofZn(NO₃):Si(NO₃)₂:Mn(NO₃)₂=2-X:1:X(0.01≦X≦0.10). Next, this mixedsolution is sprayed from a nozzle into a furnace heated to a temperatureof 1,500° C. while ultrasonic waves are applied thereto. Thus, the greenphosphor is fabricated.

Ba_(1-x)Al₁₂O₁₉:Mn_(x)

First, in a mixed solution fabrication process, materials, i.e. bariumnitrate (Ba(NO₃)₂), aluminum nitrate (Al(NO₃)₂), and manganese nitrate(Mn(NO₃)₂), are mixed in a molar ratio ofBa(NO₃)₂:Al(NO₃)₂:Mn(NO₃)₂=1-X:12:X(0.01≦X≦0.10). This mixture isdissolved in ion-exchange water to provide a mixed solution.

Next, in a hydration process, an aqueous base (e.g. ammonia aqueoussolution) is dropped into this mixed solution to form a hydrate.Thereafter, in a hydrothermal synthesis process, this hydrate andion-exchange water is held in a capsule made of a corrosion- andheat-resistant material, such as platinum and gold. This solution ishydro-thermally synthesized at specified temperatures under specifiedpressures for specified periods of time (e.g. 100 to 300° C., 0.2 to 10MPa, 2 to 20 hours) in a high pressure vessel, using an autoclave, forexample.

Thereafter, the compound is dried to provide a desiredBa_(1-x)Al₁₂O₁₉:Mn_(x). The phosphor obtained by this hydrothermalsynthesis process has particle diameters ranging from approx. 0.1 to 2.0μm and spherical shapes. Next, these particles are annealed in air attemperatures ranging from 800 to 1,100° C., and classified to providethe green phosphor.

(3) Red Phosphor

(Y,Gd)_(1-x)BO₃:Eu_(x)

First, in a mixed solution fabrication process, materials, i.e. yttriumnitrate (Y₂(NO₃)₂), hydro nitrate gadolinium (Gd₂(NO₃)₃), boric acid(H₃BO₃), and europium nitrate (Eu₂(NO₃)₃) are mixed in a molar ratio asan oxide of 1-X:2:X (0.05≦X≦0.20) and a ratio of Y:Gd=65:35. Next, thismixed solution is heat-treated in air at temperatures ranging 1,200 to1,350° C. for two hours and classified to provide the red phosphor.

Y_(2-x)O₃:Eu_(x)

First, in a mixed solution fabrication process, materials, i.e. yttriumnitrate (Y₂(NO₃)₂) and europium nitrate (Eu(NO₃)₂) are mixed in a molarratio of Y₂(NO₃)₂: Eu(NO₃)₂=2-X:X (0.05≦X≦0.30). This mixture isdissolved in ion-exchange water to provide a mixed solution.

Next, in a hydration process, an aqueous base (e.g. ammonia aqueoussolution) is added to this mixed solution to provide a hydrate.

Thereafter, in a hydrothermal synthesis process, this hydrate andion-exchange water is held in a container made of a corrosion- andheat-resistant material, such as platinum and gold. This mixture ishydro-thermally synthesized at temperatures ranging from 100 to 300° C.,under pressures ranging from 0.2 to 10 MPa, for 3 to 12 hours, in a highpressure vessel, using an autoclave, for example. Then, the obtainedcompound is dried to provide a desired Y_(2-x)O₃:Eu_(x).

Next, this phosphor is annealed in air at temperatures ranging from1,300 to 1,400° C. for two hours, and classified to provide the redphosphor. The phosphor obtained by this hydrothermal synthesis processhas particle diameters ranging from approx. 0.1 to 2.0 μm and sphericalshapes. These particle diameters and shapes are suitable for forming aphosphor layer having excellent light emission characteristics.

Conventionally used phosphors are used for phosphor layers 110R and 110Gof the above PDP100. Used for phosphor layer 110B are phosphor particlesin which quadrivalent ions substitute for part of Mg or Al ionsconstituting the phosphor. Especially, the conventional blue phosphorhas more degradation than the blue phosphor of the present invention ineach process, and thus the color temperature of white tends to decreasewhen the three colors emit light at the same time.

For this reason, in a plasma display device, the color temperature ofwhite display has been improved by decreasing the luminance of phosphorcells of colors other than blue (i.e. red and green), using circuits.However, the use of a blue phosphor of the present invention increasesthe luminance of blue cells and decreases luminance degradation in thepanel manufacturing process. This eliminates the need of intentionallydecreasing the luminance of the cells of other colors and thus the needof intentionally decreasing the luminance of the cells of all thecolors. Therefore, because the luminance of the cells of all the colorscan fully be utilized, the luminance of the plasma display device can beincreased while the color temperature of white display is kept high.

The blue phosphor of the present invention can be applied to fluorescentlighting that is excited by ultraviolet light to emit light in a similarmanner. In this case, a phosphor layer including conventional bluephosphor particles that is applied to the inner wall of a fluorescenttube is replaced with a phosphor layer in which quadrivalent ionssubstitute for Mg or Al ions.

Application of the present invention to fluorescent lighting in thismanner can provide fluorescent lighting having a luminance andresistance to luminance degradation more excellent than those ofconventional fluorescent lighting.

In order to evaluate the performance of a plasma display device of thepresent invention, samples based on the preferred embodiment wereproduced and performance evaluation tests were performed on the samples.The experimental results are described below.

Each of the plasma display devices was produced to have a diagonal sizeof 42 in. (HDTV screen having a rib pitch of 150 μm). Each of the plasmadisplay devices was produced so that the dielectric glass layer was 20μm thick, the MgO protective layer was 0.5 μm thick, and the distancebetween the display electrode and the display scan electrode was 0.08mm. The discharge gas charged into the discharge space essentiallyconsists of neon and contains 5% of xenon gas mixed therein.

In the blue phosphor particles of Sample Nos. 1 though 10 used for theplasma display devices, quadrivalent ions substitute for Mg or Al ionsconstituting respective phosphors. The synthesis conditions are shown inTable 1.

TABLE 1 Amount Quadrivalent element Amount of Amount of Sample of EuManufacturing substituting for Al or Eu Manufacturing Mn ManufacturingNo. x, y method Mg/Amount (%) X method X method Blue phosphor[Ba_(1−x)MgAl₁₀O₁₇:Eu_(x]) Red phosphor [(Y, Gd)_(1−x)BO₃:Eu_(x]) Greenphosphor [Zn_(2−X)SiO₄:Mn_(]) 1 X = 0.03 Hydrothermal Ti 0.1% X = 0.1Solid-phase reaction X = 0.01 Spray method synthesis method method 2 X =0.05 Solid-phase reaction Zr 0.2% X = 0.2 Spray method X = 0.02Hydrothermal method (Flux method) synthesis method 3 X = 0.1 Spraymethod Si 0.5% X = 0.3 Aqueous solution X = 0.05 Solid-phase reactionreaction method method 4 X = 0.2 Aqueous solution Hf 1.0% X = 0.15Hydrothermal X = 0.1 Solid-phase reaction reaction method synthesismethod method Blue phosphor [Ba_(1−x−y)Sr_(y)Al₁₀O₁₇:Eu_(x]) Redphosphor [Y_(2−x)O₃:Eu_(x)] Green phosphor [Ba_(1−x)Al₁₂O_(19:)Mn_(x)] 5X = 0.03 Solid-phase reaction Sn 1.0% X = 0.01 Hydrothermal X = 0.01Hydrothermal y = 0.1 method (Flux method) synthesis method synthesismethod 6 X = 0.1 Hydrothermal Si 3.0% X = 0.1 Spray method X = 0.02Spray method y = 0.3 synthesis method 7 X = 0.1 Spray method Ge 2.0% X =0.15 Aqueous solution X = 0.05 Solid-phase reaction y = 0.5 reactionmethod method 8 X = 0.2 Solid-phase reaction Ti, Si X = 0.2 Solid-phasereaction X = 0.1 Solid-phase reaction y = 0.3 method 1.0%, 1.0% methodmethod 9 ″ Solid-phase reaction Ce 1.0% ″ Solid-phase reaction ″Solid-phase reaction method method method 10  X = 0.1 Solid-phasereaction Ti, Zi X = 0.15 Aqueous solution X = 0.01 Hydrothermal y = 0.5method 1.0%, 1.0% reaction method synthesis method *11  ″ Solid-phasereaction None ″ Aqueous solution ″ Hydrothermal method reaction methodsynthesis method *Sample No. 11 shows a comparative example.

With reference to Table 1, for each of Sample Nos. 1 through 4,(Y,Gd)_(1-x)BO₃:Eu_(x) red phosphor, Zn_(2-x)SiO₄:Mn_(x) green phosphor,and Ba_(1-x)MgAl₁₀O₁₇:Eu_(x) blue phosphor are used in combination. Themethod of synthesizing the phosphors, the substitution ratios of Eu andMn mainly emitting light, (i.e. the substitution ratios of Eu to theelements Y and Ba and the substitution ratio of Mn to the element Zn),and the kind and amount of quadrivalent ions (element) substituting forMg or Al are changed as shown in Table 1.

For each of Sample Nos. 5 through 10, Y_(2-x)O₃:Eu_(x) red phosphor,Ba_(1-x)Al₁₂O₁₉:Mn_(x) green phosphor, andBa_(1-x-y)Sr_(y)Al₁₀O₁₇:Eu_(x) blue phosphor are used in combination.Similar to the above case, the conditions for the method of synthesizingthe phosphors, the substitution ratios of the elements mainly emittinglight, the kind and amount of quadrivalent ions (element) substitutingfor Mg or Al ions constituting the blue phosphor are changed as shown inTable 1.

Phosphor ink used for forming a phosphor layer is prepared by using eachkind of phosphor particles shown Table 1, and mixing the phosphor, aresin, solvent and dispersion agent. According to the measurementresults, viscosity of each kind of the phosphor ink (at 25° C.) is keptwithin the range of 1,500 to 30,000 CP. According to observations ofeach phosphor layer formed, the phosphor ink is uniformly applied to theside faces of the barrier ribs.

As for the phosphor particles used for a phosphor layer of each color,those having an average diameter ranging from 0.1 to 3.0 μm and amaximum diameter up to 8 μm are used in each sample.

Sample No. 11 shows a comparative example using conventional phosphorparticles in which no special treatment is performed on the phosphorparticles of each color.

EXPERIMENT 1

Model experiments were performed on Sample Nos. 1 through 10 and SampleNo. 11 (a comparative example) to determine luminances and luminancedegradation factors. In the model experiments, these phosphors werefired (520° C., 20 min.) in the rear panel manufacturing process todetermine how the luminance of each color changed. The luminance of theparticles before firing and the luminance of the applied paste afterfiring were measured. The luminance degradation factor of each colorbefore and after firing was measured.

EXPERIMENT 2

Measured was the luminance degradation factor of each phosphor beforeand after the panel assembly step (sealing at 45° C. for 20 min.) in thepanel manufacturing process.

EXPERIMENT 3

When each panel was lit in each color, a luminance and luminancedegradation factor were measured as follows. Discharge sustain pulses ata voltage of 200V and at a frequency of 100 kHz were applied to eachplasma display device continuously for 100 hours, luminances of eachpanel was measured before and after the application of the pulses, and aluminance degradation factor (([luminance after application−luminancebefore application]/luminance before application)*100) was determined.

Addressing failure at address discharge was determined by existence offlickers in an image. If flickers were found even only in one position,it was recognized as having flickers. As for the luminance distributionof each panel, a luminance was measured with a luminance meter whenwhite color was displayed and the distribution on the entire surface wasshown.

Shown in Table 2 are results of the luminances and the luminancedegradation factors of each color in these experiments 1 through 3.

TABLE 2 Luminance Luminance Luminance degradation factor degradationfactor degradation factor (%) of phosphor after (%) of phosphor (%) ofphosphor application of fired (520° C.) when panels discharge Existenceof Luminance in rear panel are sealed sustain pulses addressing at bluemanufacturing (450° C.) in panel (200 V, 100 kHz, failure at display onSample process assembly process 100 hours) address the entire No. BlueRed Green Blue Red Green Blue Red Green discharge cd/cm² 1 −0.5 −1.2−4.9 −2.8 −2.6 −13.0 −2.4 −4.4 −14.5 Not exist 80.4 2 −0.7 −1.3 −4.0−2.1 −2.4 −13.2 −2.3 −4.1 −14.2 ″ 83.2 3 −0.4 −1.4 −4.5 −2.5 −2.3 −12.9−2.4 −4.0 −14.6 ″ 89.5 4 −0.3 −1.4 −4.7 −2.0 −2.2 −12.7 −2.0 −4.2 −14.1″ 89.4 5 −0.4 −1.5 −4.9 −2.2 −2.0 −12.9 −2.2 4.3 −14.8 ″ 87 6 −0.8 −1.2−4.3 −2.4 −2.3 −12.6 −2.1 −4.1 −14.9 ″ 90.1 7 −0.6 −1.4 −4.5 −2.2 −2.4−12.3 −2.5 −4.2 −14.7 ″ 88.5 8 −0.5 −1.2 −4.3 −2.5 −2.5 −12.5 −2.3 −4.3−15.1 ″ 92.5 9 −0.4 −1.5 −4.1 −1.8 −2.1 −12.8 −3.9 −4.1 −15.6 ″ 93 10−0.5 −1.3 −4.2 −1.9 −2.3 −13.0 −1.8 −4.1 −14.8 ″ 89.4 *11 −5.5 −1.5 −4.1−21.5 −2.1 −13.2 −35 −4.1 −15.6 Exist 45.8 *Sample No. 11 shows acomparative example.

As shown in Table 2, for Sample No. 11 in which substitution ofquadrivalent ions is not performed in the blue phosphor, the luminancedegradation factors in each process are large. Especially for the bluephosphor, a luminance degradation factor of 5.5% is seen in the phosphorfiring process, 21.5% in the sealing process, and 35% in an accelerationlife test (200V, 100 kHz). In contrast, for Sample Nos. 1 through 10,all the degradation factors of the blue phosphors are 3% or smaller.Additionally, no addressing failure is found.

This is because quadrivalent ions (element) (Ti, Zi, Hf, Si, Ge, Sn, orCe) have substituted for Mg or Al ions (element) constituting a bluephosphor and this substitution has drastically reduced oxygen vacancy inthe blue phosphor (especially oxygen vacancy in the vicinity of a Ba—Olayer). This prevents defective layers (oxygen vacancy in the vicinityof the Ba—O layer) on the surface of the phosphor from adsorbing waterincluded in the ambient atmosphere in firing the phosphor or water inMgO or barrier ribs, sealing frit, and the phosphor in sealing panels.

EXPERIMENT 4

Model experiments were performed on phosphors in which quadrivalent(element) ions had not substituted for Mg or Al (element) ions in bluephosphors thereof. The phosphors were left in an atmosphere at atemperature of 60° C. and a relative humidity of 90% for 10 min., anddried at a temperature of 100° C. Then, temperature-programmeddesorption gas chromatograph-mass spectrometry (TDS analysis) wasperformed on these phosphors. The analyses show that the peaks ofphysically adsorbed water (approx. 100° C.) and chemically adsorbedwater (300 to 500° C.) are ten times as high as those in the samplessubjected to substitution (Sample Nos. 1 through 10).

EXPERIMENT 5

Shown in the Experiment 1 are examples in which blue phosphors of thepresent invention are used in plasma display devices. A sample offluorescent lighting using a phosphor of the present invention in whichquadrivalent ions substitute for Mg or Al in a blue phosphor thereof wasproduced for fluorescent lighting excited by ultraviolet light to emitlight in a similar manner.

Phosphors of each color produced under the condition of Sample No. 7 ofTable 1 were mixed and the mixture was applied to the inner wall of aglass tube, as a phosphor layer of known fluorescent lighting, toprovide Sample No. 12. As a comparative example thereof, phosphors ofeach color produced by a conventional solid-phase reaction methodwithout substitution (see Table 1) were also mixed and applied, toprovide Sample No. 13. Table 3 shows the results.

TABLE 3 Sample Luminance Luminance degradation after No. Phosphor(cd/m²) 5,000 hours (100 V, 60 Hz) 12 Phosphor of 6,750 −1.00% SampleNo. 7 13* Phosphor of 6,600 −14.6% Sample No. 11 *Sample No. 13 shows acomparative example

INDUSTRIAL APPLICABILITY

As described above, in accordance with the present invention,substituting a quadrivalent element for the element Mg or Al in thecrystal of a blue phosphor constituting a phosphor layer can preventdegradation of the phosphor layer in each manufacturing process. Thismethod can improve luminance, life and reliability of a panel and lamp.

1. A plasma display device having a plasma display panel in which aplurality of discharge cells having one of one and a plurality of colorsare disposed, phosphor layers having a color corresponding to saidrespective discharge cells are disposed, and said phosphor layers areexcited by ultraviolet light to emit light, wherein said phosphor layershave a blue phosphor, and said blue phosphor is made of one of compoundsrepresented by Ba_(1-x)MgAl₁₀O₁₇:Eu_(x) andBa_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x), wherein 0.03≦x≦0.25 and 0.1≦y≦0.5, andcontaining at least one of Ti, Zr, Hf, Si, Ge, Sn, and Ce substitutingfor part of one of elements Al and Mg.
 2. A blue phosphor excited byultraviolet light to emit visible light, and made of one of crystalstructures Ba_(1-x)MgAl₁₀O₁₇:Eu_(x) andBa_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x), wherein 0.03≦x≦0.25 and 0.1≦y≦0.25 andwherein a quadrivalent element substitutes for one of elements Al and Mgconstituting said phosphor.
 3. The phosphor of claim 2, wherein saidquadrivalent element is at least one of Ti, Zr, Hf, Si, Ge, Sn, and Ce.4. The phosphor of claim 2, wherein a substitution value of saidquadrivalent element with respect to one of elements Al and Mg rangesfrom 0.01 to 3.0%.
 5. A method of manufacturing a phosphor comprising: amixed solution fabrication step of mixing one of a metal salt and anorganometallic salt containing elements constituting a blue phosphorcomprising Ba, Mg, Al, Eu, Ti, Zr, Si, Ge, Sn and Ce and an aqueousmedia to fabricate a mixed solution; and a step of drying the mixedsolution and thereafter firing a dried mixture in a reducing atmosphereto produce one of phosphorsBa_(1-x)(Mg_(1-a)M_(a))(Al_(1-b)M_(b))Al₁₀O₁₇:Eu_(x) (wherein M and isone of Ti, Zr, Hf, Si, Ge, Sn and Ce, and wherein 0.03≦x≦0.25,0.1≦y≦0.5, a≦0.001 and b≦0.03).
 6. A method of manufacturing a phosphorrepresented by the formula Ba_(1-x)MgAl₁₀O₁₇:Eu_(x), wherein0.03≦x≦0.25, comprising: mixing in an aqueous medium salts of Ba, Mg, Aland Eu to form a hydrate, said salts mixed in a molar ratio sufficientto provide said phosphor; subjecting the hydrate to a hydrothermalsynthesis reaction at temperatures ranging from 100° to 350° C. underpressures ranging from 0.2 to 25 MPa to form the phosphor; and annealingthe phosphor at temperatures ranging from 1,000 to 1,600° C. in anatmosphere containing nitrogen and hydrogen.
 7. The method of claim 6,wherein 0.01 to 3% of elements Mg and Al in the phosphor can besubstituted with one or more quadrivalent element selected from thegroup consisting of Ti, Zr, Hf, Si, Sn, Ge and Ce by adding a salt ofsaid quadrivalent element to said aqueous medium.
 8. A method ofmanufacturing a phosphor represented by the formulaBa_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x), wherein 0.03≦x≦0.25 and 0.1≦y≦0.5,comprising: mixing in an aqueous medium salts of Ba, Sr, Mg, Al and Euto form a hydrate, said salts mixed in a molar ratio sufficient toprovide said phosphor; subjecting the hydrate to a hydrothermalsynthesis reaction at temperatures ranging from 100° to 350° C. underpressures ranging from 0.2 to 25 MPa to form the phosphor; and annealingthe phosphor at temperatures ranging from 1,000 to 1,600° C. in anatmosphere containing nitrogen and hydrogen.
 9. The method of claim 8,wherein 0.01 to 3% of elements Mg and Al in the phosphor can besubstituted with one or more quadrivalent element selected from thegroup consisting of Ti, Zr, Hf, Si, Sn, Ge and Ce by adding a salt ofsaid quadrivalent element to said aqueous medium.